The probe into a National Oceanic and Atmospheric Administration (NOAA) study of Earth temperatures is also light on actual allegations of substantial wrongdoing, Johnson wrote late Thursday.

Johnson said that in Smith’s four-month investigation, he has accused top NOAA scientists of scientific misconduct, accused the staff of the journal Science of participating, and accused the White House and NOAA of conspiring against it.

“And all of these indictments are conjured out of thin air, without you presenting any factual basis for these sweeping accusations — exposing this so-called ‘investigation’ for what it truly is: a witch hunt designed to smear the reputations of eminent scientists for partisan gain,” Johnson wrote in her letter.

She disagreed with Smith’s insistence that the Constitution justifies his investigation.

“The Constitution doesn’t provide you with a blank check to harass research scientists with whose results you disagree,” Johnson said.

She also accused him of using “discredited climate denial tactics” in his efforts to smear NOAA, its leader Kathryn Sullivan and Commerce Secretary Penny Pritzker.

In response to Johnson’s letter, Smith accused her of ignoring his efforts to crack down on Obama administration misconduct, like the mine wastewater spill earlier this year and an alleged meth lab found in a federal facility.

“The ranking member has repeatedly shown she is not interested in investigating government waste,” Smith said in a statement. “Partisan political allegiance to the Obama administration should never trump the Science Committee’s crucial oversight role or taxpayers’ best interests.”

Smith has been investigating a NOAA study published this summer that disproved the notion that global warming has “paused” for more than 15 years, an argument that climate change skeptics like Smith have long held onto.

He has subpoenaed NOAA for internal communications among scientists, even after the agency provided multiple briefings, the data behind its findings and other efforts to explain how it reached its conclusions.

Smith doubled down on his accusations Friday morning in a speech to a conservative foundation in Texas.

NOAA’s “employees altered historic climate data to get politically correct results in an attempt to disprove the hiatus in global temperature increases,” he told the Texas Public Policy Foundation. “The American people should be suspicious of the motives of this administration as it continually impedes congressional oversight of agency actions tied to extreme climate agenda.”

In a Wednesday letter, Smith revealed for the first time that whistleblowers from NOAA told the committee that the “pause” research was rushed to publication.

A NOAA official said the agency’s scientific integrity office has not received any complaints about scientific misconduct related to the study, or any such complaints so far this year.